Planooraph co



I R;L,QUASS. SIGNALING SYSTEM FOR TELEPHONEEXCHANGES.

APPLICATION FILED DEC.!!. 1916.

5 SHEETS-SHEET l.

omnvw THE COLUMBIA PLANOCIRAPH 60.. WASHINGTON, D. CL 7 1 n. L QUASS. SIGNALING SYSTEM FOR TELEPHONE EXCHANGES.

APPLICATION FILED DEC.8| 1916. I I I I Patented Aug. 12,1919.

R. 1. QUASS. SIGNAUNG SYSTEM FOR TELEPHONE EXCHANGES.

APPLICATION FILED [EC-811916- '1,31 2,8 08. Patentd Aug. 12,1919.

. 5 SHEETS-SHEET 3.

1i lm enfok." fia/ph L. Quass THE COLUMBIA PLANOGRAPH can WASHINdTON. D. c.

' 'R'; L. u ss. SIGNALING SYSTEM FOR TELEPHONE EXCHANGES.

APPLICATION FILED DEC-8.1916. I

Patented Aug. 12, 1919;

5 SHEETS-SHEET 4.

28 S S S rm: COLUMBIA PLA N0 |RAPH C0 WASHINGTON, n. c.

UNITED STATES [PATEN OFFICE.

RALPH L. QUASS, OF HAWTHORNE, NEW JERSEY, ASS'IGNOR TO- WESTERN ELECTRIC COMPANY, INCORPORATED, OF YORK, N. Y., A CORPORATION OENEW YORK.

SIGNALING SYSTEM FOR TELEPHONE-EXCHANGES.

Specification of Letters Iatent.

Application filed December 8. 1916. Serial No. 135.790.

To all whom it may concern:

Be 1t known that I, RALPH L. QUAss, a

citizen of the United States, residing at Hawthorne, in the county of Passaic and State of New Jersey, have invented certain new and useful Improvements inSignaling Systems for Telephone-Exchanges,- of which exact description.

the following is a full, clear, concise, and

This invention relates to a signaling sys' tem for telephone exchanges, and its principal object is to provide an organization for I.

effecting the automatic display of signals when certain conditions arise that call for ing systems is handled by teams or groups.

of operators to the position of any one of whom any call originating in a large group of telephone lines may be directed. In the particular call distributing system in con nection with which the present inventionis disclosed, when a call is initiated by any line of the group of lines, automatic switching mechanism acts to extend the circuit of,

the calling line to any one of the positions of the group of positions that may at the time be in condition to receive and attend to a call. \Vhile the operator is occupied in attending to a call or in supervising one of the existing connections on her position, the position is automatically made busy and unavailable to other calls that may be initiated. Vhen the trafiic is particularly heavy, the condition may arise where'all of the operators positions are busy and un-' available, and when such a condition exists, the calls are delayed or held up until one of the busy positions becomes available.

It is the principal object of the presentfinvention to provide signals that will be dis-,

played before the operators of a group,

when calls are waiting on the lines as aTre-.

sult ofthe operators being unavailable, which will apprise the operators ofthat condition and cause'them to speed up so that their positions may become available for caring for the waiting calls. The invention also has for its object the provision of signals that will be automatically displayed Patented Aug. 12,1919.

upon the arising of certain emergency conditions in the apparatus, which conditions call for special action on the board attendants.

The manner in which the foregoing and otl erob'jects are attained will be set forth in the following description and in the draw ings to which the description refers.

The specific and preferred form in which the invention in the present instance is embodied is illustrated in the accompanying sheets of drawing, in which Figures 1, 2, '3, 4, and 5, taken together, and arranged side by side as indicated by the lines that extend to the margins of the sheets, illustrate a telephone system of the call-distributing type containing the invention.

As illustrated in the drawing, the system is represented as comprising telephonelines extending from stations, as A and A, to stationary terminals upon a line finder frame G, these stationary terminals being adapted to be. connected with by a plurality part of the switch? of line finder switches or elevators, as LF and LF. Each line has associated-with it a line, relay 12 and a cut-off relay 11, and each of the groups of lines into which thewhole number of lines served by the finder frame are divided has associated with it certain group apparatus,[as LG and LG.

tus ofthe group of finder circuits as F, F" and F associated with the line finder:

switches or elevators which serve the whole group of lines. Thefinder circuits 'F,-F and F terminate in cord selector switches or elevators, as CS and. OS, and through the medium. of these, operatingunder the control of the operators selecting circuit apparatus SF, the finder circuits are adapted to have their connections extended to anyone of the connecting cord circuits which extend in conductors 85,86, 87 and '88 to the various operators positions, as 'O and O; V The operators"selecting apparatus SF, common to the entire group of finder circuits, is brought into cooperative relation with the apparatus of the finder circuits through the medium'of The group apparatus is connected through the nections for a secondcord selector frame,

together with the common operators selecting apparatus for that'frame, being lndlcated at SF.

The call-waiting pilot signals are present in the form of the lamps 256 (see Fig. 5), one of which is located at each operators position. The energizing circuit for these signals is completed'through the agency of the relay 250 under the control of the relay 251, the circuit of relay 251 in turn being controlled by relays 252 and The relays 251, 252 and 253 also control the energizing circuit of a special emergency lamp 254. One of the energizing circuits that operates through the medium of relay 250' to bring about the lllumination of the callwaiting pilot lamps 256 is designated 66 and is controlled in the-contacts of a series of relays 240, 239, 2&4 and 183. The relay 240 opens the circuit when an abnormal condition exists in the starting apparatus for the line finder switches. The relay 239 closes the circuit when a. call is waiting in any of the groups oflines served by the particular finder frame the circuits of which are illustrated, and when the holding up of the call is not due to inoperativeness in the controlling circuits. The relay 244 closes the energizing circuit 66 for the call-waiting pilot signals when all of the operators of the grou are busy, when all of the finder circuits of the group are busy, or when there is trouble in the operators selecting apparatus associated with the finder circuits. The relay 133 opens the energizing circuit 66 when the holding up of the call is due either to all of the finder circuits being busy, or to trouble in the operators selecting circuit.

The other energizing circuit that operates through the medium of relay 250 to bring about the illumination of the call-waiting pilot lamps 256 is designated 150, and is controlled in thecontacts of relays 253 and 280. The relay 253 closes the circuit of conductor 150 when a call is waiting in one of the group of finder circuits at a time when all of the operators positions are unavailable, and relay 280 opens this circuit when there is trouble in the operators selecting circuit.

The manner in which the above-menlongitudinally movable shaft 1 carrying as many sets of brushes 2 as there are groups of stationary terminals to be engaged. To move the shaft up, an extension at the lower end of the shaft is brought into engagement with the constantly rotating power member 3 by means of an idler wheel operated by the up-drive magnet 32; and to move the shaft down, the extension is brought into engagement with the power member 4 by means of an idler wheel operated by the down-drive magnet 62. Normally the brushes of each of the sets 2 are held apart so as to clear the associated terminals by means of a separating cam 5 located between the innermost brushes of the set. The cam 5 is rotatably @mounted, and when rotated in one direction releases the brushes and permits them to engage the associated terminals. The tripping or releasing of the brushes is controlled by a number of trip magnets, as 16 and 17. Each of these when energized rotates an associated trip rod 6 that extends transversely to the shafts 1 and carries as many trip yokes 7 as there are finder switches in the group. The trip rod in rotating brings all of its trip yokes 7 into position to operate the brush-controlling cams 5 of the corresponding sets of brushes on all of the sets, so that whichever of the finder switches is caused to move up has that set of brushes tripped that corresponds with the particular trip magnet 16, 17, that is at the time energized. When the finder switch that has been in use is returned to its normal position, any of the associated controlling cams 5' that has been tripped is engaged and rotated in a reverse direction to separate its switch springs again and thus render them inactive. Each of the line finder and cord selector switches has associated with it a commutator 8 which comprises a. number of stationary commutator segments and a set of movable brushes carried at the top of the switch shaft 1 and cooperating with the stationary segments. This commutator serves to make and break a number of the controlling circuits in the various stages of the-upward movement of the switch shaft.

For controlling the circuits of the organization, there are employed a number of sequence switches which are shown at different points and are designated 100, 200, and

llO

300 respectively These sequence switches may be of the type disclosed in Patent 1,127,808 issued February 9, 1915 to Reyn olds and Baldwin: Each consists of an electro-magnetically controlled motor or driving mechanism and a number of associated switch cams. The switch cams associated with each of the sequence switches 100 are designated 101 to 104 inclusive; those asso ciated with each of the sequence switches 200 arev designated 201 to 222, inclusive; and those associated with each ofthe sequence switches 300 are designated 301 to306, inclusive. To each of the contacts associated with the various sequence switch cams are applied certain numerals. These numerals in the case of the cams 101, 201 and 301 indicate the only positions of the associated sequence switchin which these particular contacts are open; the numerals applied to all of the other contacts of each sequence switch indicate the only positions of the particular sequence switch in which the associated contacts are closed.

The sequence switches 100 merely act as timing switches and have'only oneresting position. The resting positions of the other sequence switches, and the stages of operation with which these positions are associated, are as follows:

Sequence switch 200.

Sequence switch 300.

1. Awaiting a call. 4. Position vacant. 17. Position busy.

The operation of the system to which in the present instance the invention is applied will first be taken up, and then the special features toward which the invention is particularly directed will be described, and,

their cooperative relation with thesystem as a whole explained.

Then a subscriber calls, the taking of the telephone receiver from'its hook closes a circuit in the usual way that causes the energization of the associated line relay 12 at the central office. Theiline relay in operating closes a circuit that extends from'battery through the winding of relay 19' of the group in which the calling line is located, contacts 103 (-18% to 171-) of sequence switch to ground. Relay 19 in operating closes a circuit that extends from battery through the right-hand Winding of relay 24, front contact and armature of relay 19, conductor 57, inner back contact and armature of relay 22, left-hand back contact and armature of relay 23, back contact and armature of relay 65 to ground. Relay 21 in operating closes a locking circuit for itself in its left-hand front contact and armature, and in doing so causes the operation of the associated tripping magnet 16, the energizing path for the tripping magnet and for the left-hand or locking winding of relay 24: beingin paral lel from battery by way of the left-hand front contact and armature of relay 24, conductor 58, winding of relay 22, left-hand armature and back contact and armature of relay 23, and back contact and annature of relay 65 to ground. Relay 241: in operating also closes a circuit that extends from battery through the motor magnet of the associated sequence switch 100, sequence switch contact 102 (18% to 1%), and right-hand front contact and armature of relay 2% to ground. The closure of this circuit moves sequence switch 100 out of position 1, whereupon theswitch continues to rotate, under the control of its governing cam 101, until it completes its cycle and again comes to rest in position 1. lVhile' the sequence switch 100 is rotating it maintains open in sequence switch contact 103 {18+} to 13;) the connec tion of the relay 19 with the group conductor 18, so that during this period the relay 19 is not under the control of the line relays 12, of the corresponding group. During this interval the calling line is found and the line relay 12 deenergized to remove the ground from the conductor 18, as hereinafter to be described.

Included in the circuit by way of conductor 58 closed upon the initiation of a call,.as described above, is the winding of the starting relay 22. This relay in operating closes the circuit of the starting conductor 29, and in doing so brings about the movement of a line finder switch of one or another of the finder circuit-s F, F or F. For reasons that will hereinafter be explained only one'of the sequence switches associated with those finder circuits is in position 2. Assuming that this is the sequence switch of finder circuit F, a circuit iscompleted that extends from battery through the left-hand winding of relay 30, sequence switch contacts 206 (2 conductor 29, inner front contact and armature of relay 22, left-hand armature and back contact of relay 23, and back contact and armature of relay 05 to ground. Relay 30 in operating closes a locking circuit for itself that extends from battery through resistance coil 56,

sequence switch contacts 217 (2 to 9), righthand winding of relay 30, sequence switch contacts 216 (2 to 4) and (2 to 9), lefthaud front Contact and armature of relay 30, and armature and back contact of relay 37 to ground. Relay 30 also closes a circuit that extends from battery through the motor magnet and cam 202 (2) of sequence switch 200, right-hand front contact and armature of relay 30, sequence switch contacts 208 (18 to 14) and (2 to 7) to ground. The closure of this circuit causes sequence switch 200 to move out of position 2 and come to rest in position 3.

In position 3 of the switch, a circuit is closed that extends from battery by way of the up-drive magnet 32 of the corresponding line finder switch LF, sequence switch con tact 207 (3 to at), front contact and righthand armature of relay 30, and sequence switch contacts 208 (18 to 1st) and to 7) to ground. The energization of the updrive magnet 32 starts the upward movement of the corresponding elevator rod with its associated sets of brushes. At the outset of the upward movement of the elevator rod all of the brush trip levers are moved past the corresponding trip yokes. The only trip magnet that is energized in this case is the magnet 10 which corresponds with the group in which the calling line is assumed to be located; and consequently the only trip yoke in position to engage a trip lever on the elevator rod is the one which controls the brushes t0, %1, -l2 and -l3 that are adapted to engage the terminals of that particular group of lines. This set of brushes therefore is released and made operative, and the other sets are held clear of their associated line terminals. 1

As soon as the set of brushes corresponding with the calling line is tripped, the group apparatus, by means of which the lines control the brush tripping and line finder starting operations, may be returned to its normal condition. The first step in this restoring operation is effected by the closure of a circuit which is completed by way of the K segment of the line finder commutator immediately after the brushes are tripped. This circuit extends from battery in parallel branches through the relays 33 and 23 (see Fig. 2), conductor 26, sequence switch contact 209 (25}; to 3), conductor 68, and to ground by way of the K segment of the line finder commutator and its associated brush. T he encrgization of the relay 23 interrupts, in the lefthand back contact of that relay, the previously described circuit that has up to this time maintained the energization of the trip magnet 16, the group relay 2t and the common starting relay 22. Relay 23 in its right-hand front contact closes a locking circuit for itself and the associated relay 33 that extends by way of sequence switch in position 2 awaiting the receipt of a call. Vhen the call comes in this sequence switch is immediately moved to position 3, in the manner described above. Therefore, at this stage of the operation, the sequence switches of all of the finder circuits, being either in position 1 or in position 3 and beyond, are in position to close their contacts 210. The locking circuit for the relays 23 and 33 is therefore held closed until another one of the finder circuits has its sequence switch moved into position 2 to break the locking circuit in the corresponding sequence switch contacts 210. This is accomplished by relay 33 which in operating applies a ground to conductor 28 to move the sequence switch of another finder circuit out of position 1 and into position 2, and which also applies a ground to the conductor 27 to move the sequence switch of the appropriated finder circuit out of position 3.

Assuming that the sequence switch of finder circuit F is in position 1, and that the sequence switch of finder circuit F is in some position between 4 and 17, that finder circuit being assumed to be in use, the operation of the relay 33 completes a circuit from battery through the motor magnet and contacts 203 (1) of the sequence switch of finder circuit F, contacts 211 (l) of the same sequence switch, contacts 211 (3 to 17 and (4 to 17) of the sequence switch 200 of finder circuit F contacts 211 (3 to 17 and (3 to 32;) of the sequence switch 200 of finder circuit F that has just been appropriated, conductor 28, and left-hand front contact and armature of relay 33 to ground. This causes the sequence switch of finder circuit F to move into position 2. At the same time the sequence switch of finder circuit F is moved out of position 3 by the closure of a circuit that extends from battery through the motor magnet and contacts 203 (3) of the sequence switch of that circuit, conductor 27, and left-hand front contact and armature of relay 33 to ground.

As soon as the sequence switch of finder circuit F moves into position 2, it opens in its contacts 210 the circuit by way of conductor 25 which up to this moment has maintained relays 23 and 33 energized, and these relays thereupon release their armatures. Relay 23in releasing reconnects to ground the circuit which extends in branches 57 and 58 through the various sets of line group relays, thus again giving the line groups access to the starting circuit.

At this stage of the operation of the system the sequence switch of the appropriated finder ircuit F is in position 4, and the elevator rod of the associated line finder LF is moving up with the set of brushes tripped that corresponds with the group in which the calling line is located. As the tripped brushes rise they come into engagement successively with the sets of terminals corresponding with the difierent lines of the group. At the instant of engagement of the brush 42 with the corresponding line terminal 46 of each line, a circuit is closed that extends from battery by way of the relay 52, sequence switchcontacts 212 (2 to 4), conductor 50, brush 42, line terminal 46, conductor 53, and Winding of cut-ofl' relay to ground. In case a line over which the brushes are passing is busy, either as a call ing or as a called line, a branch path from battery is closed to conductor 53 which serves to shunt the relay 52 and p'reventits operation as the finder brushes pass over the terminals of thecorresponding line. In the case of the lines that are not busy, the relay 52 is operated as the brushes engage the terominals of such lines. In attracting its armatures the relay 52 closes a circuit that extends from battery through the lower winding or" the relay 37 front contact and inner armature of relay 52, sequence switch contacts 213 (2 to 4), conductor 49, brush 41, line terminal 45, conductor 39 to one limb of the telephone line, thence by way of the path controlled in contacts of the substation switchhook to the other limb of the line, conductor 38, terminal 44, brush 40, conductor 48, sequence switch contact 214 (2 to 4), upper armature and front contact of the relay 52, and upper winding of the relay 37 to ground. The circuit traced above is not completed until the finder switchbrushes engage the terminals of the calling line, for the reason that the calling line is the only line that has its telephone receiver oif the hook and at the same time is not made busy by being connected with either by some other line finder or by a connecting cord calling plug. The completion of this circuit energizes the relay 37 and causes that relay to interrupt in its back contact the circuit by way of the left-hand armature and front cont-act of the relay 30, sequence switch contacts 216, right-hand winding of relay30, sequence switch contacts 217, and resistance 56 to battery, which circuit has been holding relay 30 locked up from the moment that the relay was first energized upon the receipt of the call.

Relay 30 in releasing its armatures breaks its own locking circuit traced above, and also breaks the previously traced path including sequence switch contacts 208, right-hand'ar mature and front contact of the relay 30, and sequence switch contact 207, over which current has been flowing to energize the updrive magnet 32 of the line finder. Therefore the operation, of the relay 37 upon the finding of the calling line actsto efiGQtthe instant deenergizationof the up-drive magnet 32 and' thus stop the brushes upon the terminals of the calling line. l/Vhen the relay 30 is deenergiz'ed, as a result of finding the calling line, it also compl-etes a circuit that extendsfrom battery through the motor magnet and contacts 202 (3 to 4) of the sequence switch 200, righthand back contact and armature of there lay 30, sequence switch contacts 208 (18 to 14) and (2 to 7), to ground. The closure of this circuit movesthe sequence switchout of position When they sequence switch reaches positlon 4%, it closes a pathgforthe flow of current through the cut-off relay 11 of the calling line by way: of resistance coil 64, sequence switchcontact 212 (45} to 12 1:),

conductor 50, brush 42, line terminal 46 and conductor 53. The flow of currentin this path operates the cut-ofi relay 11 'to' discern nect the line relay 12 from thecircuit,'and that relay, in releasing its armature disconnects ground fromv the common conductor 18, f The disconnection of ground from conductor 18 occurs before the timing sequence switch 100 has completed its'cycle of rotation and reconnected conductor 18 with relay.19. 3 I

hen the finder sequence switch {200 reaches position 5, it "closes a circuit that.

extends from battery" by wayf'o f the. winding of relay 55 (see Fig. '4), conductor 71, and sequence switch contact 218 to 8) to ground. The operationofthe relay 55 applies ground to'the conductors-81 extending tion thus closing-a circuit over which the position relay 92 may be energlzed'to render that operators position selectable. 7

If the operator is listening in ona cord, the switch 415 associated with that cordcircuit is closed'in any suitable manner and; an energiz ng circuit completed for relay 91.

Likewise, if all of the coimecting'cords of a a particular operators position are in use, the entire series of switches .416, one of which is associated witheach connecting cord-circuit of the position, as is more clearly shown and described in the patent to S. B. Williams, Jr.,-No. 1,304,641 of May 27, 1919, are closed and the relay 194'ener- I gized to complete an energizing circuit for the relay 91. In either case, the energization of the relay 91 renders the operators position unselectable. Furthermore, when the operator is away from her station, the switch 122 is operated, in any usual or con- Kiri venient manner, to complete a circuit'that extends from battery, through the motor magnet and contact 303 (1 01'17) of the sequence switch 300, to ground by way of the resting contact and left-hand switch spring of the switch 122. The closure of this circuit moves the sequence switch to position 4, in which position sequence switch contact 30-1 (1) is open, and the position is consequently rendered unselectable. When the operator takes her station, the levels of switch 122 are moved to the right, and a circuit is com pleted for the motor magnet of sequence switch 300 by way of contact 303 (i) and the alternateconta'ct and right-hand switch lever of switch 122,wh ich causes the sequence switch to move to position 1, its next resting position. In this position of the sequence switch the operators position, subject to the control of relay 91, is rendered select able by the closure of sequence switch contact 304:

At each position where the relay 91 is inert and the sequence switch 300 is in posit-ion 1, as described, a circuit is closed that extends from battery, through the winding of associated relay 92, armature and back contact of relay 91, sequence switch contact 301 (1), conductor 81, left-hand armature and front contact of relay 55, to ground. The relay 92 of each such awaiting or available position, therefore, attracts its armature and closes a circuit that extends from battery, tl'irough the front contact and armature of relay 92, to the conductor 82, and thence to ground by way of the windings of the relays 77 at the various cord selector frames as SF and'SF.

The finder circuit sequence switch 200 does not stop in position 5, but continues its movement and comes to rest in position 6. Here it awaits the closing of a circuit the completion of which is dependent upon the condition of the other finder circuits of the associated group. This circuit extends from battery, through the left-hand winding of the relay. 30, contact 219 (6) of the appropriated finder circuit sequence switch, contacts 219 (9 to 1) of the sequence switches of the associated finder circuits preceding it in the series, conductor 76, outer armati'lre and back contact of relay 5st, and right-hand back contact and armature of relay 61 to ground. This circuit is open either in cam 219 of a preceding finder sequence switch 200 in the series or in contacts of the relays 54 or 61 as long as any other sequence switch of the series is in positions a to 9. That is, it is open from the time the line finder switch of any associated finder circuit finds a calling line until the cord finder switch of that circuit has moved far enough to trip the brushes corresponding with the selected group, thus completing the operators selection. Not until this has occurred, will. the

above traced circuit of the awaiting finder circuit be closed.

When this circuit is closed relay 30 attracts its armatures and completes a circuit that extends from battery, through the motor magnet and sequence. switch contact 202 of the sequence switch 200, front contact and right-hand armature of relay 3'0, and sequence switch contacts 208 (18 to lit) and (2 to 7) to ground. The comple tion of this circuit moves the finder sequence switch out of position 6.

lVhen the finder sequence switch reaches position 6%, it closes a circuit that extends from battery, through the winding of relay 5%, left-hand back contact and armature of relay 61, conductor 78, and finder sequence switch contact 218 (6% to 8) to ground. Relay 5a attracts its armature and completes a branch of the circuit. just traced, which extends from conductor 73 by way of the armature and back contact of the relay 63, front contact and left-hand armature of relay 54L, armature and front contact of the first relay 77 that is energized as previously described, as a result of the corresponding operators position being in readiness to receive a call, right-hand back contact and switch spring of relay93 of the corresponding group, Winding of associated relay 94, winding of relay 93, left-hand switch spring and back contact of relay 93, conductor 83, left-hand back contact and armature of relay 95 at the corresponding operators position, to battery. Upon the closure of the above traced branch circuit, the group relays 93 and 9a are energized in parallel with the relay 54. Relay 93 in operating disconnects its own energizing winding and that of associated relay 94: from the previously traced path to battery by way of the left-hand back contact and armature of the relay 95, and

connects them in a path which extends from.

battery by way of the winding of the relay 95 and conductor 81. This causes the relay 95 also to be energized and to interrupt in its left-hand armature and back contact the path by way of conductor 83 over which the relays 93 and 94: were initially energized. Relay 95 also closes a circuit that extends from battery by way of the motor magnet and contact (1) of the operators sequence switch. right-hand front contact and armature of relay 95 and right-hand c0ntact and lever of switch 122 to ground. The closure of this circuit moves the operators sequence switch through position 1 and to position 17, where it remains until its motor magnet is energized by the operation of switch 192 or of switch 122, switch 192 being operated in any convenient manner when it is desired to restore the availability of this position for receiving calls, and switch 122 being operated when the operator leaves the position.

Relay 94 in operating closes a circuit from battery, through the winding of the trip magnet 20 corresponding to the selected operators position, and to ground by way of the right-hand armature and front contact of the relay 9 1. This relay also closes a circuit that extends from battery, through the winding of the relay 63 and the lefthand armature and front contact of the relay 9t to' ground. The relay 63 in operating closes a branch that extends from the conductor 73 (grounded at contact 218 (6% to 8) of the line finder sequence switch),

through the armature and front contact of relay 63, conductor 72, sequence switch contact 220 (7), and left-hand winding of relay .30 to battery. Relay attracts its armaerating is locked up over a circuit that extends from battery, through resistance 56,

sequence switch contacts 217 (2 to 9), righthand winding of relay 30, sequence switch contacts 216 (7 to 9) .and (2 to 9), front contact and left-hand armature of relay 30 and armature and back contact of relay 37 to A ground.

When the sequence switch reaches position 8,.it closes a circuit that starts the upward 30, sequence switch contact 218 (8 to 9), and r thence to ground. At the outset of the upward movement of the cord selectorbrush rod, the tripping levers of the various sets of brushes are brought simultaneously into operative position with respectto the corresponding trip yokes, and that set of brushes is tripped and made operative whose trip magnet is at the time energized. In the present instance, it is assumed that this is the trip magnet 20 associated with the terminals of the group of connecting cord circuits extending to the O operators position.

Immediately after the set of brushes is tripped the common operators selecting circuit is restored so as to be available for the use of other cord finder switches. This is effected through the medium of a circuit that is completed by the grounding ofthe K segment of the cord finder commutator, this segment being so located as to be engaged by its brush immediately after the tripping levers of the sets of brushes pass the associated tripping yokesh The circuit referred In moving out of position 8, the sequence energizes the corresponding trip magnet 22 and the common relay 63. The de'energization of the relayv 93 reestablishes, subject 30 to the release of relay 61, the control of other finder circuits over the brush-tripping mechanism of the associated cord finder frame.

Relay 61 in operating closes a locking circuit for itself by way of conductor 7 3, sequence switch contact 218 to 8), and

thence to ground. Italso completes a circuit that extends from battery through the motor magnet and contact 205 (8) of the sequence switch 200, conductor 75, righthand front contact and armature of relay 61 to ground. The closure of this circuit moves sequence switch 200 out of position 8.

95 switch opens its contacts 218 (6%to 8) and Y221 (72 1308), thus deenergizing relay 61 and again extending conductor 73 to the relay 54: and the conductors over which the op erators selectionis effected. In closing its right-hand back contact upon release, relay 61 also restores the continuity of conductor 76 and makes it. available for moving out of position 6 the sequence switch of some other finder circuit which may be waiting for access to the operators selecting circuit.

When the sequence switch .200 is moved out of position 8, it movesinto position 9 and there awaits the finding ofan idle connectingicord circuit upon the operatofis position that has been selected. .As' the brush-carrying rod moves up, the brushes 111, 112, 113 and 114: of the setthat has been tripped come into engagement with sets 7 of terminals 115, 116, 117 and 118 corres'ponding' with the different connecting cord circuits located at that operators position. When a cord ci "cuit is not in use, itscorresponding terminal 118 is connected directly to ground; and when the terminals of such 120 a connecting circuit are encountered, a path is completed that extends from battery,

through the lower winding of relay 37, sequence switch contacts206 (8 to 9), con- .ductor 99, brush 11 1, terminal 118-, conductor 88 of the cord circuit, contact 161, which is closed when the associated cord is not in use, and back contact and armature of relay 119 to ground. Current flowing in this cir cuit causes the relay 37 to attract its arn1a- 1 ture and break the previously traced. circuit by way of sequence switch contacts 216 and 217 and the right-hand winding 01? relay 30 which, up to this time, has been holding relay 8O energized. hen the relay 30 is released, it opens, in its right'hand front contact, the previously traced circuit including the up-drive magnet 34, and thus causes the brushes of the cord finder switch to come to rest on the terminals of the selected cord circuit. The relay 30 in releasing also closes a circuit that extends from battery through the motor magnet and contact 202 (9) of the sequence switch 200, back c011- tact and right-hand armature of relay 30, and sequence switch contact 218 (8 to 9) to ground. The closure of this circuit moves the sequence switch 200 out of position 9, whereupon it moves under the control of its cam 201 into position 14, which is the talking position of the finder circuit.

The connecting circuit to which the finder circuit is extended is illustrated in the pres ent instance as being a cord-circuit terminating in a connecting plug 170 and including in its talking conductors S5 and 86 the windings of a repeating coil 169 with a bridged battery, and the usual signal controlling relays 171 and 187. The connecting circuit also includes a ringing key 120 by means of which current from the ringing generator 181 may be applied to the circu1t of the called line, and a listening key 130 by means of which the connection of the operators telephone set 147 with the called line may be controlled.

The extension of the finder circuit to the connecting cord brings about, in a manner which need not be described, the actuation of a signal on the associated operators position which informs the operator that a call is waiting. The operators telephone is connected with the circuit by means of the listening key 130; and when the operator has learned the number of the line with which the calling subscriber desires connection, she completes the connection by inserting the calling plug 17 0 into the springjack 14 of that line. Before the plug is inserted, a busy test may be made in the usual way over the path that is shown extending from the tip of the plug by way of the armature and back contact of the relay 175. lVhen the plug is inserted, a circuit is closed that extends from battery through the winding of the relay 119, winding of the relay 175, the cooperating sleeve contacts of the calling plug 17 0 and springjack 14:, and the winding of the cut-off relay 11 to ground. The completion of this circuit causes all three relays to attract their armatures, the relay 119 opening the path to ground of conductor 88, thus rendering the connecting cord circuit uuselectable, lay l7 disconnecting the cf the plug 179 from the test conductor and completing the talking circuit of the tip strand, and the cut-0E relay 11 disconnecting the line relay 12 from the called su bscribers line. Ringing current from the ringing generator 181 may then be applied to the called subscribers line by closing the contacts of the ringing key 120.

By means of mechanism which is disclosed in the patent to S. B. lVilliams, Jr., No. 1,301,641 of May 27, 1919, and which it is unnecessary to describe as it forms no part of the present invention, the extension of the finder circuit to the connecting cord-circuit brings about the opening of the contacts of the switch 161 and the closing of the con tacts of the switch 152. The switch 152 corresponds to the left-hand armature and front contact of relay 152 of the above-mentioned WVilliams patent and the switch 161 corresponds to cam 104 of the sequence switch too of the said lVilliams patent. The switch 161 in opening its contacts renders the associated cord-circuit unselectable immediately and in advance of the opening of the contacts controlled by the relay 119. The closing of the contacts of switch 152 completes a circuit that extends from battery through the winding of relay 155, switch contacts 152, conductor 87, contact 117 and cooperating brush 113 of the cord selector, conductor 98, contacts 217 (9% to 1% and 12 to it) of the finder sequence switch, right-hand Winding of relay 30, sequence switch contact 212 (12% to 14), conductor 50, brush 12 and contact 46 of the line finder, conductor 53 and winding of cut-oil relay 11 of the calling subscribers line to ground. The current that flows in this circuit keeps the relays 155, 30 and 11 energized during the time that the connection is established. The relay 155 closes a normal break in the ring strand 86 of the talking circuit. The relay 30, as long as it is energized, prevents the finder sequence switch 200 from moving out of its talking position 1 1. The cut-oil relay keeps the branch by way of the line relay 12 disconnected from the calling line.

At the termination of the conversation, the replacing of the telephone receivers on their switchhooks at the calling and called subscribers stations brings about the display of supervisory signals (not shown) which may be controlled by the cord-circuit relays 171 and 187 in the usual way, and the operator in response to this indication withdraws the calling plug 170 from the springjack of the called subscribers line. The withdrawal of the plug is accompanied by the opening of the contacts of switch 152. This opens the circuit traced in the preceding paragraph including the relays 155, 30 and 11, and these relays release their armal'i i-ti'en' 39 at the finder circuit releases, it closes a circuit that extends from battery through the motor magnet and contact 202 (8 to 1 1) of the finder sequence switch, left-hand back contact and armature of relay 30, and armature and back contact of relay 37 to ground. This moves the finder sequence switch out of the talking position 14. When the finder sequence switch reaches position 15, it is moved through that position by means of a circuit that is completed from battery, through its motor magnet and contact 202 (15), righthand back contact and armature of relay 30, sequence switch contacts 218 (15) to ground. When the line finder sequence switch reaches position 16, a circuit is completed that extends from battery through the down-drive magnet 62 of the line finder switch, and sequence switch contacts 208 (16) to ground. As a result, the brushes of the line finder switch are returned to normal.

)Vhen the brushes reach their normal position, a circuit is closed that extends from battery, through the motor magnet and contact 205 (16) of the finder sequence switch, conductor 69, segment Y of the line finder commutator and its corresponding brush to ground. This moves the finder sequence switch out of position 16. In the next resting position 17 of the finder sequence switch, a'circuit is closed that-extends from battery through the down-drive magnet 35 of the cord selector switch, conductor 90, and sequence switch contact 218 (17 to ground. The closure of this circuit energizes the down-drive magnet 35 and causes'the cord selector brushes to return to their normal position. At the end of the downward movement of the brushes,- a circuit is closed that extends from battery through the motor magnet and contact 205 (17) of the finder sequence switch, conductor 31, Y segment of the cord selector commutator and corresponding brush to ground. The completion of this circuit moves the finder sequence switch 200 out of position 17, after which it returns to position 1 under the control of its cam 201. a I

It has been necessary in the foregoing to describe the normal operation of the call distributing system in order that the application of the present invention in its preferred form to such a system, and the cooperative relation that exists between such a call distributing system and the call-waiting pilot and special signaling part of the organization may be fully understood. This part of the organization will now be de' scribed.

The call.waiting pilot signals are in the form of lamps 256 located at the various operators positions of the group, and the controlling circuits and apparatus associated with these lamps are so organized that the lamps may be lighted only when calls are being held up by all of the operators positions being in use or unavailable. When a call is delayed or held up,-that condition brings about the operation of the relay 232 (see Fig. 1) associated with the particular group or subdivision of lines "in which the calling line is located. The actuation of the line relay 12, that results from the taking of the telephone receiver from its'hook at the substation, applies a ground to the con ductor 18 and in so-d'oing closes a circuit from battery through the lower winding of the relay 232 and to groundat the armature and contact of the line relay." But in thenormal operation of the system,-theactua-' tion of the line relay 12 is immediately fol lowedby the closure of theenergizing cir-' cuit of the timing sequence switch 100 in: the right-hand armature and contact ofxthe group relay 24:; and the timing sequence switch, in moving outof its normal or 1i .position, closes a circuitthat extends from battery through the upper winding ofthe relay; 232, timing sequence switch contact 104: (2 to 18) to groundby way of the armatureand front contact of the line relay; 12. 'The 'relay 232-is differentially wounchwith the result that the currents flowing in the two windings neutralize each other, andthe C1I- cuits controlled in the-armatures :and contacts of the relay 232 are notco npleted.

Butif the actuation of therline-relay 12"isnot followed promptly by the movement of the timing sequence switch 100, only-the lower Winding of the relay 232is energized, and the contacts controlled bythatrelay. are: closed. As a result, acir'cuit is completed: that extends from battery, through vthe winding of relay 239, left-ha1id contact and armature. of relay 237, and upper contactand armature ofv relay 232 of the, group in which the calling line is located, to ground. This energizes the relay 239 and closes one of the two normal breaksv in the controlling circuit 66 of'the call-waiting pilotsignals.

As has previously been described, when an operator is not at her position, the operators sequence switch 300 is standing in po sition 4L and the sequence switch contact 305' (4) is closed. When the operator isather energized to energize the relay 1 93, and thus cause the latter relay to 'keep its contacts closed. When one or another of these con ditions exists at all of the operators positions of the group of positions, a circuit is completed that extends from battery, through the winding of relay 134 (see Fig. 2), conductor .79, and either the sequence switch contact 305 (4 or the closed cont-acts of relay 193 at each operators position of the series, to ground at the end of the series. This energizes relay 134:, which completes a circuit that extends from battery, through the winding of relay 140 and the front contact and armature of relay 13% to ground. Relay 140 completes a circuit that extends from battery, through relay 214, and the front contact and armature of relay 140 to ground. This energizes relay 24-1, which attracts its armature to. close the other normal break in the. controlling circuit 66, thus permitting current to flow from battery, through the right-hand winding of relay 250 (see Fig. 5), conductor 66, outer armature and back contact of relay 133 (Fig. 2), front contact and armature of relay 2&4, front contact and armature of relay 239, and back contact and armature of relay 240 to ground. This causes relay 250 to attract its armature and close a circuit that extends.

from battery in parallel through the callwaiting pilot lamps 256 of all of the operators positions of the group, front contact and armature of relay 250, and back contact and armature of relay 251 to ground. Thus when the condition of a call awaiting in any of the groups coincides with the condition of all of the operators of the associated operators group being busy or unavailable, the call-Waiting pilot signals at all of the operators positions are actuated.

The blocking of the calls from access to l the finder circuits when all of the operators positions areeither vacant or busy is effected through the medium of the relay (see Fig. When all of the positions are thus unavailable, the energizing circuit of the relay 134: is closed and the relay 1341- causes the actuation of relay 1&0, as previously described. lVhen relay 140 operates, it closes a circuit that extends from battery, through the winding of relay 136, and to ground by way ofthe front contact and armature of relay 14:0. Relay 136 in operating closes a circuit that extends from battery by way of the armature and lower front contact of relayl36', winding of relay 65, and to ground by way of the outer back contact and armature 0t starting relay 22. Relay 136 also closes a circuit that extends from battery by way of the armature and upper front contact of that relay and through the winding of the slow-acting relay 139 to ground. The relay 139 operates and in its contacts closes a branch circuit from battery for the energization of relay 65.

When the relay 65 operates, it closes at its front contact a locking circuit to ground for continuing its energization, and at its back contact disconnects ground from. the series-group system of conductors that includes the conductors 57 and 58 and contacts and winding of the starting relay 22.

the common starting relay and the relays 19 and 24 and trip magnet 16 of each of the groups complete their energizing circuits, is disconnected. This prevents any calling line of any of the groups from having control over i group apparatus or over the starting relay Consequently, as long as this condition continues, any line in calling closes a circuit through the lower winding of relay 232, but does not cause the movement of the timing sequence switch 100 to close a circuit through the upper or neutralizing winding of relay 232, and hence the relay operates to energize relay 23. asdescribed.

WVhen the call-waiting pilot signalsare displayed, the operators know that calls are being held up, and consequently make an effort to put their positions in a receptive condition. 'The first position that becomes available brings about the interruption of conductor 79 at the sequence switch contact 305 or the contact of relay 193 of that position. The breaking of conductor 7 9 causes the deenergization of relay 13l, that causes the deenergization of relay H0, that causes the deenergization of relays 136 and 139, which causes the blocking relay 65 to fall back and reapply ground to the series group circuit by way of the starting relay 22. The deenergization of relay 1 10 also causes the relay 21% to fall back, thus opening the circuit of conductor 66 to bring about the deenergization of relay 250 to cause the extinguishing of the call-waiting pilot lamps 256. As soon as an operators position becomes available, therefore, the awaiting call is given access to the finder circuits, and the call-waiting pilot signals before the operators are Withdrawn.

In connection with the relays 232, there is provided certain apparatus which operates to give an emergency alarm signal when a call is held up as a result of an ab normal condition of the circuits or apparatus over which the calling line has access to the finder switches. This apparatus includes a slow-acting train of relays 23 t, and 236, a relay 237. the energizing circuit of which is controlled by the slow-acting relay train, group lamps 231, a common lampcontrolling relay 138 and a. release key 238. When the relay 232 attracts its armatures, it closes a circuit that extends from battery, through the winding of relay 23st, righthand back contact and armature of relay 236, armature and back contact of relay 233, armature and back contact of relay 151, and upper front contact and armature of relay to ground. The relay 23a attracts its armature and closes a branch of the above traced circuit that extends from battery,

energizing path of the relay 234. The lastnamed relay releases its armature and opens the energizing circuit of the relay 235, which relay in turn releasesv its'armature and completes a circuit that extends from battery, through the left-hand winding of relay 237, left-hand armature and front contact of relay 236, back contact and armature of relay 235, armature and back contact of relay 233,

armature and back contact of relay 151, and upper front contact and armature of relay 232 to ground. The relays 231'and. 235 are constructed and adjusted so as to release their armatures slowly, as a result of which an appreciable interval elapses from the application of the ground at the upper contact and armature of relay 232 until the circuit is completed through the slow-acting train to the left-hand winding of relay 237. Consequently, unless the continuity of the path to ground is broken within this time interval, the relay 237 is energized and closes a circuit that extends from battery,

through the lamp 231 of the group with which the operated relay 232 is associated, right-hand armature and front contact of relay 237, normally closed contacts of release key 238, and to ground by way of the common lamp-controlling relay138- The up-. per armature and front contact of relay 237 also closes a locking circuit for that relay by way of its right-hand winding, the two windings of relay 237 being cumulative in their effect. In response to the lighting of the common lamp controlled byrelay 138 and the group lamp 231, the attendant may take appropriate action, and then press the release key 238, which breaks the locking circuit through the right-hand winding of relay 237 and opens the alarm signal circuit. I In the normal operation of the system, the relay 232 may remain operated for a considerable length of time while awaiting the freeing of the series-group circuit, including the conductors 57 and 58, and the starting circuit by calling lines in groups preceding its associated group in the series. In such a case, the starting relay 22 is being kept energized by the calls in the preceding groups in the series, as a result of which an energizlngcircuit is completed for relay 151 by way of the outer front contact and armature of relay 22. Consequently relay 151 maintains open the previously described circuit through the slow-acting relay train so that the energizing circuit of relay 237 is not completed to light the emergency lamps.

In like manner, if the relay 232 is held actuated for a considerable interval due to the breaking of the ground path by Way of the back contact and armature of the blocking relay 65, on account of all of the operators positions being unavailable, the circuit for energizin the emergency lamp controlling relay 237 by way of the slow-acting relay train is broken at the contacts of the relay 233, which relay has its energizing circuit completed by Way of the'contacts of relay 140, which relay, as previously described, is actuated by the energization of relay 13 1'when all of the operators positions are unavailable. Thus the relay 237 cooperates with a relay 232 to light the associated lamps only when the protracted operation of the relay 232 is due to some abnormal condition of the circuit orapparatus; Obviously, under such circumstances, the call that is being held up could not reach the operators even if they should speed up in order to take it; and for this reason the'relay 237 is so arranged that when it operates to light the emergency lamps, it also breaksthe energizing circuit of the relay 239 so as to prevent the completion of the controlling circuit for the call-waiting pilot lamps.

In the normal operationofthe system, the

.be prevented froin'having access to the finder circuits and would therefore be, held up. under such circumstances it is ime possible for the waiting" calls to reach the operators positions, it is desirable that the call-waiting pilot signals shall not be lighted. The prevention of the signals from lighting is accomplished 'through th e mediumof the relay 240 andthe slow-acting relay train 241, 2&2, 213'. The operation of this slow-acting train, which has its circuit togroundcompleted by way of the'front contact and outer armature of starting relay 22, is exactlyfthe same as the operation of the slow-acting train 234, 235 and 236 previously described; As a result,,if the starting relay 22 fails to release within the predetermined noi'mal' interval, a circuit is completed that extends from battery, through the winding of relay'2 10, the contacts of relays2a3 and 2&2 of the slow-acting train, and the outer front contact and armature of relay22 to ground. f The closure of this circuit causes relay 24-0 to attract its armature and open the controlling circuit 66 of the call-waiting pilot signals.

If all of the 'linefinder circuits that serve the lines of a finder frame are in'use, it is desirable that additional calls initiated by the lines shall be blocked. This is accomplished by means of a circuit that extends from battery, through the winding of relay 135, conductor 80, and finder sequence switch contacts 215 (4: to 17) of all of the finder circuits in series, to ground at the end of the series. hen all of these sequence switch contacts are closed as a result of all the finder circuits being in use, the relay 135 is energized and completes a circuit for energizing: relay 133. That relay in turn completes the energizing circuit of relay 1 10, relay 110 completes the energizing circuit of relay 136, relay 136 completes the energizing circuit of the blocking relay 65, and that relay opens the ground connection of the starting relay 22 and the series group conductors 57 and 58, thus depriving all of the lines of the various groups of control over their associated group apparatus and the common starting apparatus. But under these circumstances, where the calls are blocked as a result of no finder circuits being available, it is desirable that the call-waiting pilot signals at the operators positions be not actuated. Therefore, the relay 133 in operating is arranged to open at its outer back contact and armature the circuit of the conductor 66, thus preventing the operation of relay 250 and the lighting of the callwaiting pilot lamps. Y

Another condition under which it is. desirable to block the calls and prevent them from having access to the finder circuits, but undesirable to give the operators the callwaiting pilot signal, is that in which there is trouble or an abnormal condition in the operators selecting circuit. Such a condition leads to the energization of the relay 280 (Fig. 4:), in a manner hereinafter to be described, and that relay in operating closes a circuit that extends from battery by Way of th winding of relay 133 (Fig. 2), con- ,ductor 78, and front contact and armature of relay 280 to ground. Relay 133 in operating acts through the medium of relays 140,

136 and 65, in a manner previously described, to disconnect ground from the starting relay 22 and the series group conductors 57 and 58, thus depriving calling lines of control over the group and startlng apparatus. Relay 133 at the same time opens, in its outer armature and back contact, the circuit of conductor 66, thus preventing the waiting calls from energizing the relay 250 to operate the callwaiting pilot signals 256.

The manner in which an abnormal condition in the operators selecting circuit brings about the energization of the relay 280 to operate relay 133 is as follows: The circuit which controls the access of the finder cir cuits to the common operators selecting apparatus is the circuit that extends serially through the sequence switch contacts 219 (9 to at) of all of the finder circuits of the group. This circuit is normally closed, and

in, the normal operation of the system is open only while a finder circuit is being served by the operators selecting apparatus. Included in the normallyclosed circuit is the relay 273 which is kept energized by the normal current flow in this circuit. hen the circuit by way of the sequence switch contacts 219 (9 to t)- is opened, this relay is deenergized, releases its armature and permits the closure of the associated contacts. But the relay 273 is made slow releasing, as by providing its core with a copper. sheath, so that the closure. of the asso ciated contacts occurs a certain interval after the energizing circuit is broken. lVhen the contacts of the relay 27 3 close, a circuit is completed that extends from battery, through the left-handwinding of the relay 280, and thence to ground by way of the switch contacts of the relay 273. But in the normal operation ofv the system, the opening ofthe circuit in the finder sequence switch contacts 219, when the sequence switch moves out of position l, is followed promptly by the grounding of conductor 73, by way'of contacts 218 (6% to 8) of the finder sequence switch when the sequence switch moves out of position 6 and connects the corresponding finder circuit with the common operators selecting circuit. The grounding of conductor 7 3- completes a circuit that extends from battery, through the winding of 'relay 281, conductor 73, andsequence switch contacts 218 (651- to 8) to ground. Relay 281 thereupon attracts its arinatures and closes. a circuit that extends 'from battery, through the winding of relay 27 3, left-hand armature and front contact of relay 281, and right-hand armature and front contact of relay 55 to ground, the last mentioned relay having been energized by way of conductor 71 and finder sequence switch contacts 218 (5 to 8) whenthe sequence switch moved into position 5. The interval required by the slow-acting relay 273 to release its armature and close its circuit is made a little longer than the interval required in the normal operation of the system for the sequence switch to move to position 6% and energize relay 281. As a result, the relay 281 normally acts to close the alternative energizing circuit for the relay 273 before the relay 273 has had time to respond to the opening of its normal energizing circuit by way of conductor and the series of sequence switch contacts 219 But if. the opening of the circuit by wayof conductor 70 is not followed within this definite interval by the closure of the alternative energizing circuit by way of the contacts of relay 281, then the relay 273 permits the closure of its contacts, and the energization of relay 280 follows. Or if, at the time the finder sequence switch moves into position 6%; and operates relay 281, the

relay 55 for any reason is not energized, then the alternative energizing circuit for relay 273 will not be completed and the relay 280 will be operated.

In the normal operation of the system, each finder circuit should have connection with the common operators selecting circuit only for a sufiiciently long interval to permit the selection of an operators position, the starting of the brush-carrying elevator and the tripping of the brushes. At the moment any finder circuit is connected with the common operators selecting apparatus through the medium of conductor 7 3, the relay 281 is energized by way of the circuit extending to ground through contact 218 (6% to 8) of the corresponding finder circuit sequence switch, as previouslydescribed. When the relay 281 operates, it applies a ground'to the energizing circuit net-work of the train of slow-acting relays 282, 283, 284C and 285. As a result, the relay 282 operates and closes the energizing circuit for the relay 283, the relay 283 operates and closes the energizing circuit for the relay 284, the relay 284: operates and closes the energizing circuit for the relay 285, the relay 285 looks up and also opens the energizing circuit of the relay 282-, that relayreleases slowly and opens the energizing circuit of the relay 283, the relay 283 releases slowly and opens the energizing circuit of relay 28%, the relay 28st releases slowly and closes a circuit that extends from battery through the right-handwmding of relay 280, left-hand armature and front contact of relay 285, back contact and armature of relay 28%, and right-hand front contact and armature of relay 281 to ground, thus energizing relay 280 to accomplish the results hereinbefore referred to. The relays of this slow-acting train, and of the other slow-acting trains previously described, are

organized and operate in the manner disclosed in Patent 1,163,896 to Darrah, issued December 14, 1915. The time intervals 1nvolved in the operation of this train of relays, in order finally to close the energizing circuit of the relay 280, are, in the aggregate, greater than the interval required for the finder sequence switch to move from position 65}; toposition 8 in the normal operation of the system. Therefore, if the system is operating normally, the relay 281 is denergized and releases its armatures before the circuit closed by way of its right-hand armature and front contact has existed long enough to effect the closure of the branch including the right-hand winding of the re lay 280. But if, for any reason, any finder circuit holds the commonoperators selecting circuit for an unduly long interval, then the relay 280 is energized to block the calls and prevent the operation of the call-wait ing pilot signals.

The system also provides for the display of the call-waiting pilot lamps 256 when a call is waiting in any of the finder circuits at, a time when all of the operators positions are unavailable. This result is accom: plished through the medium of relay 250 and its energizing circuit 150. As has previously been described, when a call reaches a finder circuit and arrives at the stage where an operators position is to be selected, the relays 77 of all of the operators positions that are available are energized, and a moment later the finder sequence switch closes its contact 218 (6% to 8), to ground the conductor ,73 and energize the relays 93 and 9% corresponding with the first operators positlon in the series that is available. But 1f all of the operators positions are unavailable at the time when the finder sequence switch reaches its 6% position, all of the relays 77 are inert, and a circuit is completed that extends from battery, through the winding of relay 253, conductor 149, back contacts and arinatures of all of the relays 77 in series, inner armature and front contact of relay 54:, back contact and armature of relay 63, back contact and armature of relay .61, conductor 73, and contact 218 (6% to 8) of the finder circuit, sequence switch to gro-Lmd. This energizes relay 253 and completes a circuit that extends from battery, through the left-hand Winding of relay 250, right-hand front contact and armature of relay 253, and back contact and armature of relay 280 to ground. This energizes the relay 250 and closes the circuit for the illumination of the call-waiting pilot lamps 256, as already described.

It will be noted that the energizing circuit of relay 250 by way of conductor 150, is controlled in resting contacts of the relay 280. This is so that in case the call is being held up in the finder circuit as a result of an abnormal or inoperative condition of the operators selecting circuit, the resultant energization of the relay 280, as already described, will open the circuit of conductor 150 and prevent the energization of relay 250 to light the call-waiting pilot lamps.

A further control of the call-waiting pilot lamps 256 is effected through the agency of the relay 251 and its energizing circuit. The relay 251 is energized by the operating of the relay 253 at a time when the relay 252 is inert. That is, it is operated when the entire series of relays 77 in the operators selecting circuit is inert at a time when one or more of the operators positions, as indicated by the condition of their sequence switch contacts 305, are really available. WVhen an operators position is available, the associated sequence switch 300stands in potion 1. As soon as the operator receives a call or supervises a connection or leaves her station or has connections up on all of her cord circuits, the sequence switch of her station moves either into position '17 or into position a, as already described. When all of the positions become unavailable and all of the sequence switches 300 are moved out of position 1, a circuit is completed that extends from battery, through the winding of slow-acting relay 252, conductor 143, and the series of sequence switch contacts 306 (2 to 18) to ground at the end of the series. The resultant energization of the relay 252 opens the energizing circuit of relay 251, so that that relay is not operated to prevent the lighting of the call-waiting pilot lamps when the relay 253 operates to display these signals. But if due to an abnormal or inoperative condition of any of the relays 77 in the operators selecting circuit, the series circuit by way of the resting contacts and armatures of these relays is closed for the energization of the relay 253 at a time when one or more operators positions are in fact available, then the sequence switch'contacts 306 corresponding with such available positions will be open, thus interrupting the continuity of the energizing circuit of relay 252 and permitting the contacts of that relay to remain closed. As a result, the operation of the relay 253 closes the energizing circuit of the relay 251, which relay in attracting its armature opens the energizing circuit for the call-waiting pilot lamps 256 and closes a circuit extending from battery through a common alarm relay 255, emergency lamp 254, nd front contact and armature of relay 251 to ground. The energization of the alarm relay 255 and the lighting of emergency lamp 254 apprises the attendant of the nature and location'of the abnormal condition that had arisen in the circuits.

. In order that the features toward which this invention is directed may be fully and clearly'disclosed, it has been necessary to describe them in connection with other features that are the subject of co-pending applications assigned to the same assignee, such applications including the applications of SB. Williams, Jr., Serial No. 75,328, filed January 31, 1916, Serial No. 75,329, filed January 31, 1916, Serial No. 107,090, filed July 1, 1916, Serial No. 133,701, filed November 27, 1916, (Case. 22) joint application of S. B. Williams, J1"., and R. L. Quass, Serial No. 131,089, filed November 13, 1916, (Case 21-5); and application of 1*. A. Stearn, Serial No. 107 ,540, filed July 5, 1916. Such other features are the subject of claims in the applications mentioned above, and are not claimed in the present application.

What is claimed is:

1. The combination with a group of operators positions, of a. group of circuits for extending calls thereto, signaling means for said operators positions, and means made operative when all the positions of said group are unavailable to bar calls from said groupof circuits and to actuate said signal ing means upon the initiation of a call.

2. The combination with a group of operators positions, of a group of circuits for extending calls thereto, signaling means for said operators positions, means responsive to the unavailable condition of all the positions of the group for barring calls from said group of circuits and rendering said signaling means operable, and means actuated in the initiation of a call when all the positions are unavailable for operating said signaling means.

The combination with a plurality of telephone lines and a plurality of operators positions, of a plurality of call-extending circuits for connecting said lines with said positions, a. signal at each operators position, means responsive to the initiation of a call by any of said lines for actuating said signals, and means operated by the extending of said call to a. call-extending circuit for preventing the actuation of said sig- 'nals.

at. The combination with a plurality of telephone lines and a plurality of operators positions, of a line relay associated with each line, switching mechanism controlled thereby for extending the circuit of a calling line to an operators position, electromagnetic mechanism rendered operable by the operation of any of said line relays and prevented from operating by the operation of said switching mechanism, and a plurality of signals, one at each operators position, under the control of said electromagnetic mechanism.

5. In a telephone system, the combination with calling telephone lines, of line relays for said lines and switching mechanism controlled thereby for finding said lines, and an electrical emergency device rendered operable by the operation of any of said line relaysand prevented from Operating by the operation of said switching mechanism.

6. In a telephone system, the combination with calling telephone lines, of line relays for said lines and switching mechanism controlled thereby for finding said lines, a relay having 'an energizing circuit closed by the operation of any of said line relays, means made operative in the operation of said switching mechanism for rendering said energizing circuit ineliective, and slow-acting electrical emergency mechanism controlled by said relay.

7. In a telephone system, the combination with telcphone'lines, of a line relay for each line, switching mechanism controlled by said relays for extending the circuit of a calling line, a differentially wound relay, an energizing circuit for one of the windings of said relay closed by the operation of any of said line relays, an energizing circuit for the other .winding of said differential, relay closed in the operation of said switching mechanism, and slow-acting electricalemergency mechanism responsive to the operation of saiddifterential relay. 7

8. The combination with aplurality oftelephone lines, of a line relay for each actuated by the correspondingline in calling, a plurality of operators positions, switching mechanism responsive to the actuation of any of, said relays for extending the circuit of the associated line to an idle operators position, slow-acting electrical emergency mechanism also responsive to the actuation of any of said relays, means made operative in the operation of said switching mechanism for preventing-the operation of said emergency mechanism, and means re-' sponsive to the busy condition of all of said positions for rendering said switching mechanism and said emergency mechanism inoperative.

9. The combination with a plurality of telephone lines, of a line relay for each actuated by the corresponding line in calling,

a plurality of operators positions, a signal at each position, switching mechanism responsive to the actuation of any'of said relays for extending the circuit of the associated line to an idle operators position, slow-acting electrical emergency mechanism also responsive to the actuation of any of said relays, means made operative in the operation of said switching mechanism for preventing the operation 7 of said emergency mechanism, means responsive to the busy condition of all of said positions for rendering said switch mechanism and said emergency mechanism inoperative and said signals operable, and means responsive to the actuation of any of said relays for operatin said signals.

10. in a telephone system, the combination with telephone lines and operators positions, of switching mechanism for extending the circuit of said lines to said operators positions, signaling means for said operators positions, means responsive to the unavailable condition of all of said positions for rendering said signaling means operable, an emergency signal, means actuated by. any of said lines incalling for causing the operation of said switching mechanism, and means responsive to delayed operation of said switching mechanism for causing the operation of either said signaling means or said emergency signal.

11. The combination with a plurality of operators positions and a plurality of findei circuits for extending calls thereto, of an operators selecting circuit associated with said finder switches, a switch at each operators position closed when the associated position is unavailable, a switch, in said operators selecting circuit for each position adapted to be closedwhen the. corresponding position is unavailable, an emergency signahand means for actuating the same made operative by the closure of all of said switches in the operators selecting circuit at a time when all of said switches at the operators positions are not closed.

12. The combination with a group of telephone lines, a group of operators positions, and a group of trunk circuits for extending the circuits of said lines to said positions, of signaling means for said positions, means jointly responsive to the initiation of a call by'fany of said lines and the unavailable condition of said operators positions for actuating said signaling means, and means responsive to the; busy condition of all of said trunk circuits for preventing the actuation of said signaling means.

13. The combination with a plurality of telephone lines, a plurality of operators positions, and a plurality of trunk circuits for interconnecting the same, of call-waiting signaling means for said positions, means jointly responsive to the initiation of a call by any of said lines and the unavailable condition of said operators positions for actuating said signaling means, an operators selecting circuit controlling the access of said trunks to said operators positions, and means responsive to an abnormal condition in said operators selecting circuit for preventing the actuation of said signaling means.

14:. The combination with a pluralityof telephone lines, a plurality of operators positions, and a plurality of finder circuits for interconnecting said lines and positions, of a signal for each position, means actuated jointly by the initiation of a call by any of said lines. and the unavailable condition of said operators positions for operating said signals, starting mechanism controlled by any of said lines in calling and controlling the interconnecting operation of said finder circuits, and means responsive to an abnormal condition of said starting mechanism for preventing the energization of said signals.

15. The combination with a group of operators positions, of means for extending calls thereto, operators selecting apparatus associated with said call-extending means and responsive' to the available or unvailable condition of corresponding operators positions, a device at each operators position responsive to the available or unavailable condition of the associated position, signaling means for said operators position, an energizing circuit for said signaling means under the olnt con- 7 trol of said operators selecting apparatus and 

